Electronic devices in general and power amplifiers in particular, that are common in many electronic devices such as radio base stations, operate with limited efficiency. Therefore a significant fraction of their power consumption turns into heat. It follows that the thermal design of these devices is important. Such devices are typically air-cooled and their mechanics serve as thermal interface between the hot devices and the air. The heat-generating source, such as a power amplifier transistor or microprocessor, typically attains its thermal contact with the heat-dissipating device by bolting or soldering. The heat-dissipating device can be a cooling flange or heat sink with or without active cooling such as a fan. Heat sinks function by efficiently transferring thermal energy (“heat”) from an object at high temperature to a second object at a lower temperature with a much greater heat capacity. This rapid transfer of thermal energy quickly brings the first object into thermal equilibrium with the second, lowering the temperature of the first object, fulfilling the heat sink's role as a cooling device. Efficient function of a heat sink relies on rapid transfer of thermal energy from the first object to the heat sink, which is designed to efficiently dissipate thermal energy to the surrounding air.
Traditionally, the heat-generating device is soldered to a substrate such as a printed circuit board (PCB) as well. In operation, heat generation will cause both the PCB and the cooler to expand. Since they normally are made of different materials, the magnitude of expansion will be determined by their respective coefficients of thermal expansion. A flange, heat sink, is typically made of metal such as aluminum or copper and will therefore expand more than a PCB which is typically made of plastic laminate or other similar materials. A flange might alternatively be made of an alloy. This difference will impart a force on the connection between the PCB and the cooling flange. Ultimately it will also impart a force on the solder joints between the heat-dissipating device and the PCB that it sits on, since transistors and other heat-generating devices are attached to both the PCB and the cooling flange. As the component work load varies during operation, the temperature will cycle causing variation in the mentioned force, which will lead to stress on the connection points.
Experience has shown that this stress will cause the solder joints to fail prematurely, requiring the soldered component or even the complete device to be replaced. This is a costly process, in addition to the interruption of operation. The stress effect is even more pronounced if there is more than one component with significant heat generation in the device.
Patent document U.S. Pat. No. 6,128,190 A describes a transistor clamp provided to obviate solder joints and stress imparted hereon. However not all components are suited for this solution. Due to their design or for other reasons, some components require soldering or similar fixing methods.